用途说明
service命令用于对系统服务进行管理，比如启动（start）、停止（stop）、重启（restart）、查看状态（status）等。相关的命令还包括chkconfig、ntsysv等，chkconfig用于查看、设置服务的运行级别，ntsysv用于直观方便的设置各个服务是否自动启动。service命令本身是一个shell脚本，它在/etc/init.d/目录查找指定的服务脚本，然后调用该服务脚本来完成任务。
看看下面的手册页可能更加清楚的了解service的内幕：service运行指定服务（称之为System V初始脚本）时，把大部分环境变量去掉了，只保留LANG和TERM两个环境变量，并且把当前路径置为/，也就是说是在一个可以预测的非常干净的环境中运行服务脚本。这种脚本保存在/etc/init.d目录中，它至少要支持start和stop命令。
man service 写道 service(8) service(8)
NAME
service - run a System V init script
SYNOPSIS
service SCRIPT COMMAND [OPTIONS]
service --status-all
service --help | -h | --version
DESCRIPTION
service runs a System V init script in as predictable environment as possible, removing most environment vari-
ables and with current working directory set to /.
The SCRIPT parameter specifies a System V init script, located in /etc/init.d/SCRIPT. The supported values of
COMMAND depend on the invoked script, service passes COMMAND and OPTIONS it to the init script unmodified. All
scripts should support at least the start and stop commands. As a special case, if COMMAND is --full-restart,
the script is run twice, first with the stop command, then with the start command.
service --status-all runs all init scripts, in alphabetical order, with the status command.
FILES
/etc/init.d
The directory containing System V init scripts.
ENVIRONMENT
LANG, TERM
The only environment variables passed to the init scripts.
SEE ALSO
chkconfig(8), ntsysv(8)
Jan 2006 service(8)
常用方式
格式：service <service>
打印指定服务<service>的命令行使用帮助。
格式：service <service> start
启动指定的系统服务<service>
格式：service <service> stop
停止指定的系统服务<service>
格式：service <service> restart
重新启动指定的系统服务<service>，即先停止（stop），然后再启动（start）。
格式：chkconfig --list
查看系统服务列表，以及每个服务的运行级别。
格式：chkconfig <service> on
设置指定服务<service>开机时自动启动。
格式：chkconfig <service> off
设置指定服务<service>开机时不自动启动。
格式：ntsysv
以全屏幕文本界面设置服务开机时是否自动启动。
使用示例
示例一 网络重启
当修改了主机名、ip地址等信息时，经常需要把网络重启使之生效。
[root@node34 root]# service network
用法：/etc/init.d/network {start|stop|restart|reload|status}
[root@node34 root]# service network status
配置设备：
lo eth0
当前的活跃设备：
lo eth0
[root@node34 root]# service network restart
正在关闭接口 eth0： [ 确定 ]
关闭环回接口： [ 确定 ]
设置网络参数： [ 确定 ]
弹出环回接口： [ 确定 ]
弹出界面 eth0： [ 确定 ]
[root@node34 root]#
示例二 重启MySQL
[root@node34 root]# service mysql
mysql: unrecognized service
[root@node34 root]# service mysqld
用法：/etc/init.d/mysqld {start|stop|status|condrestart|restart}
[root@node34 root]# service mysqld status
mysqld (pid 1638) 正在运行...
[root@node34 root]# service mysqld restart
停止 MySQL： [ 确定 ]
启动 MySQL： [ 确定 ]
[root@node34 root]#
示例三 service脚本源码展示
[root@web ~]# cat /sbin/service
#!/bin/sh
. /etc/init.d/functions
VERSION="`basename $0` ver. 0.91"
USAGE="Usage: `basename $0` < option > | --status-all | \
[ service_name [ command | --full-restart ] ]"
SERVICE=
SERVICEDIR="/etc/init.d"
OPTIONS=
if [ $# -eq 0 ]; then
echo "${USAGE}" >&2
exit 1
fi
cd /
while [ $# -gt 0 ]; do
case "${1}" in
--help | -h | --h* )
echo "${USAGE}" >&2
exit 0
;;
--version | -V )
echo "${VERSION}" >&2
exit 0
;;
*)
if [ -z "${SERVICE}" -a $# -eq 1 -a "${1}" = "--status-all" ]; then
cd ${SERVICEDIR}
for SERVICE in * ; do
case "${SERVICE}" in
functions | halt | killall | single| linuxconf| kudzu)
;;
*)
if ! is_ignored_file "${SERVICE}" \
&& [ -x "${SERVICEDIR}/${SERVICE}" ]; then
env -i LANG="$LANG" PATH="$PATH" TERM="$TERM" "${SERVICEDIR}/${SERVICE}" status
fi
;;
esac
done
exit 0
elif [ $# -eq 2 -a "${2}" = "--full-restart" ]; then
SERVICE="${1}"
if [ -x "${SERVICEDIR}/${SERVICE}" ]; then
env -i LANG="$LANG" PATH="$PATH" TERM="$TERM" "${SERVICEDIR}/${SERVICE}" stop
env -i LANG="$LANG" PATH="$PATH" TERM="$TERM" "${SERVICEDIR}/${SERVICE}" start
exit $?
fi
elif [ -z "${SERVICE}" ]; then
SERVICE="${1}"
else
OPTIONS="${OPTIONS} ${1}"
fi
shift
;;
esac
done
if [ -x "${SERVICEDIR}/${SERVICE}" ]; then
env -i LANG="$LANG" PATH="$PATH" TERM="$TERM" "${SERVICEDIR}/${SERVICE}" ${OPTIONS}
else
echo $"${SERVICE}: unrecognized service" >&2
exit 1
fi
[root@web ~]#
示例四 crond服务的源码
[root@web init.d]# cat /etc/init.d/crond
#! /bin/bash
#
# crond Start/Stop the cron clock daemon.
#
# chkconfig: 2345 90 60
# description: cron is a standard UNIX program that runs user-specified \
# programs at periodic scheduled times. vixie cron adds a \
# number of features to the basic UNIX cron, including better \
# security and more powerful configuration options.
# processname: crond
# config: /etc/crontab
# pidfile: /var/run/crond.pid
# Source function library.
. /etc/init.d/functions
. /etc/sysconfig/crond
t=${CRON_VALIDATE_MAILRCPTS:-UNSET}
[ "$t" != "UNSET" ] && export CRON_VALIDATE_MAILRCPTS="$t"
# See how we were called.
prog="crond"
start() {
echo -n $"Starting $prog: "
if [ -e /var/lock/subsys/crond ]; then
if [ -e /var/run/crond.pid ] && [ -e /proc/`cat /var/run/crond.pid` ]; then
echo -n $"cannot start crond: crond is already running.";
failure $"cannot start crond: crond already running.";
echo
return 1
fi
fi
daemon crond $CRONDARGS
RETVAL=$?
echo
[ $RETVAL -eq 0 ] && touch /var/lock/subsys/crond;
return $RETVAL
}
stop() {
echo -n $"Stopping $prog: "
if [ ! -e /var/lock/subsys/crond ]; then
echo -n $"cannot stop crond: crond is not running."
failure $"cannot stop crond: crond is not running."
echo
return 1;
fi
killproc crond
RETVAL=$?
echo
[ $RETVAL -eq 0 ] && rm -f /var/lock/subsys/crond;
return $RETVAL
}
rhstatus() {
status crond
}
restart() {
stop
start
}
reload() {
echo -n $"Reloading cron daemon configuration: "
killproc crond -HUP
RETVAL=$?
echo
return $RETVAL
}
case "$1" in
start)
start
;;
stop)
stop
;;
restart)
restart
;;
reload)
reload
;;
status)
rhstatus
;;
condrestart)
[ -f /var/lock/subsys/crond ] && restart || :
;;
*)
echo $"Usage: $0 {start|stop|status|reload|restart|condrestart}"
exit 1
esac
[root@web init.d]#